Continuous casting apparatus having mold plug



J. E. FoLDESsY 3,318,366

May 9, 1967 l CONTINUOUS CASTING APPARATUS HAVING MOLD PLUG 7 Sheets-Sheet l Filed June 19, 1964 77 l Figi n FgZ INVENTOR.

E F OLDE SSY J U S T I N ATTORNEY May 9, 1967 J. E. FOLDESSY CONTINUOUS CASTING APPARATUS HAVING MOLD PLUG '7 Sheets-Sheet 2 Filed June 19, 1964 vFig.4

INVENTOR.

J U` S T I N E F OLDESSY ATTORNEY BYMM- May 9, 1967 J. E. FOLDESSY 3,318,366

CONTINUOUS CASTING APPARATUS HAVING MOLD rPLUG 7 Sheets-Sheet Filed June 19, 1964 INVENTOR.

JUSTIN E. FOLDESSY ATTORNEY May 9, 1967 J. E. FOLDESSY 3,318,366

CONTINUOUS CASTING APPARATUS HAVING MOLD PLUG Filed June 19, 1964 '7 Sheets-Sheet 4 Fig.6

24 INVENTOR J usTlN E.FoLo|-:ssY

BY Mn @ZZZQV ATTORNEY May 9, 1967 .1.5. FoLDL-:ssv y 3,318,366

CONTINUOUS CASTING APPARATUS HAVING MOLD PLUG Filed June 19, 1964 '7 Sheets-Sheet if INVENTOR.

JUSTIN E. FOL DESSY ATTORNEY May 9, i957 .L E. FOLDESSY 3,318,366

CONTINUOUS CASTING APPARATUS HAVING MOLD PLUG 7 Sheets-Sheet C Filed June 19, 1964 INVENTOR JUSTIN E. FOLDESSY BY f5. 'f' /f Qzn/ ATTORNEY May 9, 1967 J. E. FOLDESSY 3,318,366

` CONTINUOUS CASTING AIARATUS HAV-[NG MOLD PLUG Filed June 19, 1964 '7 Sheets-Sheet 7 Fi g. l2

' INVENTOR.

J U S T IN E. F OLDESSY BY Wfl/,M

ATTORNEY- United States Patent 3,318,366 CONTINUOUS CASTING APPARATUS HAVING MOLD PLUG Justin E. Foldessy, Ogden Dunes, Ind., assigner to United States Steel Corporation, a corporation of Delaware Filed .lune 19, 1964, Ser. No. 376,317 7 Claims. (Cl. 164-274) This invention relates to apparatus for the continuous casting of metals and more particularly to devices for initially closing the lower end of the mold in continuous casting apparatus prior to the pouring of metal therein.

It is customary in the continuous casting of metals to provide an apparatus comprising a vertical tubular watercooled mold open at the upper end for receiving molten metal and open at the lower end for the discharge ofv a metal casting, a plurality of water sprays and a plurality of guide rolls below the mold for simultaneously cooling and guiding the casting as it descends, and motor driven pinch rolls located below the water sprays and guide rolls for controlling the rate of descent of the casting. The water Aspray and guide roller section is of considerable height in order to produce a substantial degree of solidication of the casting, which has only a relatively thin solidified skin as it emerges from the mold. Consequently the pinch rolls are located at a considerable distance below the bottom of the mold.

It is necessary to close the lower discharge end of the mold initially when molten metal is being poured into the mold. This is conventionally done by the insertion of a starter bar into the bottom of the mold. The starter bar is an elongated metal bar, usually solid and rigid, which has a cross-sectional shape approximately the same as that lof the mol-d with a slightly smaller cross-sectional area in order to permit ready insertion of the bar upwardly through the guide rolls and into the bottom of the mold. In addition to closing the discharge end of the mold While molten metal is being poured, the starter bar also supports the metal column or casting as it descends through the guide rolls and pinch rolls. The conventional sta-rter bar extends from the lower end of the mold to the pinch rolls when in position for pouring metal. In this way the pinch rolls are in contact with either the starter bar or the casting itself throughout the entire casting operation so as to control the rate of descent of the casting.

Because of its great length, the starter bar customarily consists of a plurality of separable sections. This sectional structure necessitates the expenditure of considerable time and labor in order to assemble a starter bar prior to its insertion upwardly through the guide rolls and into the bottom of the mold prior to the start of a casting.

In view of the time and expense required in preparing a conventional starter bar for a casting, it is `desirable to provide a short one-piece structure which can be readily inserted into a mold with a minimum of advance preparation.

It is an object of this invention to provide a one-piece plug of length substantially less than the distance between the bottom of the mold and the pinch rolls for closing the bottom of the mold prior to the start of casting.

It is a further object of this invention to provide a mechanism which is capable of supporting the novel mold plug while molten metal is introduced into the mold and controlling the rate of descent of the mold plug and casting thereafter.

A still further object of this invention is to provide a novel apparatus for positioning the mold plug prior to the start of a casting.

These and other objects Will be apparent from the specification which follows.

FIG. 1 is a front elevational view, partly in section, and

with parts broken away, of the apparatus according to one embodiment of this invention.

FIG. 2 is a side elevational view of the apparatus shown in FIG. l.

FIG. 3 is a horizontal sectional view taken along line 3-3 of FIG. 1.

FIG. 4 is a vertical sectional view taken alon-g line 4--4 of FIG. 1.

FIG. 5 is a side elevational view, with parts broken away, of a system for bringing a pre-assembled mol-d and mold closure plug according to this invention into position for pouring molten metal into the mold.

FIG. 6 is a front elevational view of the system shown in FIG. 5.

FIG. 7 is a partial front elevational view, partly in section, of an apparatus according to a modified form of the invention.

FIG. 8 is a front elevational view, partly in section, and with parts broken away, of the apparatus according to a third embodiment of the invention.

FIG. 9 is a top plan view showing in detail the motor driven roll assembly of FIG. 8.

FIG. 10 is a side elevational View of the roll assembly shown in FIG. 9.

FIG. l1 is a sectional view, partly in elevation, taken along line 11-11 of FIG. 8, and

FIG. l2 is a partial front elevational view, partly in section, of the apparatus according to a fourth embodiment of the invention.

Referring now to FIG. l, 20 indicates a vertical openended tubular continuous casting mold. The lower end of mold 20 is closed by closure plug 22 prior to the pouring of molten metal into the upper end of mold 20. Mold 20 is a conventional continuous casting mold, having cooling water channels (not shown) therein, so that the perimeter of the casting adjacent the mol-d walls is solidified while the casting is still in the mold. The lower end of the casting adjacent mold closure plug 22 also becomes solidified and becomes attached to the mold closure plug 22 as will be hereinafter described in further detail. The mold closure plug 22 and the attached casting are guided in a vertical path as they descend below the mold by means of guide rolls 24. Guide rolls 24 are journaled in roll chocks 25.

During descent of the mold plug and casting, the surfaces of the latter are cooled by means of a plurality of water sprays 26 located between adjacent guide rolls 24. The rate of descent of the casting is controlled by upper pinch rolls 28 and lower pinch rolls 3G. In certain cases the design may .incorporate one set of pinch rolls to accomplish this result.

The length of mold closure plug 22 is considerably less than the distance between the bottom of mold closure 20 and upper pinch rolls 23. In order to prevent free fall of mold closure plug 22 and the attached casting before the mold closure plug 22 reaches upper pinch rolls 28, it is necessary to provide a mechanism for controlling the rate of descent and supporting the weight of the mold closure plug and the attached casting. This mechanism in the illustrated embodiment is a chain conveyor mechanism indicated generally at 32 and comprising a pair of endless chains 34 having a plurality of lugs 36 projecting outwardly a short distance therefrom, a pair of upper sprockets 38, and a pair of lower sprockets 40. One pair of sprockets is motor driven; for convenience this may be the lower pair 40. Lower sprockets 40 are set farther apart than upper sprockets 38 to provide for disengagement of mold closure plug 22 from chains 34 when the mold closure plug reaches upper pinch rolls 28, as shown by dotted line position 22a. A pair of idler rolls 42 cause the chains 34 to travel vertically from -upper sprockets 38 to about the elevation at which upper lmold closure plug .22.

pinch rolls 28 are located, `then to travel slightly outwardly as it continues its downward tra-vel to lower sprockets 40. The axes of sprockets 38 are located outwardly from roll chocks 25, and the circumferences of sprockets 38 extend slightly inwardly of roll chocks 25. Thecenter portions of roll chocks 25 in the vicinity of. Y sprocket wheels 38 are cut away to accommodate these .lie in the same planes as the surfaces of roll chocks 25,

and are lined .with wear strips 43.

The upper end 45 of mold closure plug 22 is of ap'- proximately the same size and cross-sectional shape as the passage in mold 20, bein-g only slightly smaller so Vertically exas to permit easy insertion of the mold plug 22 into the lower end of the mold 20. The lower end 46 of mold closure plugl 22`is preferably of somewhat larger size than the upper end 45.

Mold closure plug 22 has a pair of indentations 47 in therlower portions of the sides for receiving lugs 36.y

Engagement ofvlugs 36 with mold closure plug 22 controls the rate of descent of the plug 22 andthe' attached casting and supports the superimposed weight until the plug reaches upper pinch rolls 28. Thereafter the pinch Y rolls 28 control the rate of descent and support the weight of the plug 22 and the attached casting. Indentations 47 consist of downwardly and inwardly sloping mold closure plug side 'wallsl 48 terminating in shoulders 49.1` These sloping wal-ls 48 permit entrance of lugs 36V into indentati'ons 47. 'Mold closure plug 22 has chambers 50 inthe sides and spring pressed bumper blocks 52 in chambers 50. `Bumper Vblocks 52 are biased outwardly by springs 54. Outward movement of blocks 52 is limited by retaining plates'5'6.

The upper end of plug 22 is provided with a slide plate 60 which slides in a transversely extending channel 62 `near the upper end of mold: closure plug 22. A thin metal chill plate 63 resting on the upper end of plug `22 protects plug 22 from the heat of molten metal which is poured into mold 20. An asbestos rope 63a may encircle the perimeter of chill plate63 adjacent the moldwalls so as to prevent the entrance of molten metal into the gap between the mold walls and closure plug 22. A plurality of pins64 (two are shown herein) having heads 66 about the upper surface of mold closure plug 22 with necks 68 in the-vi`cinity off slide plate 60areV welded to chill plate 63. Slide plate 60 has slots 70 havingcircular portions slightly larger than the .diameter of pins 64 `and a nan rower loblong portion for gripping pins 64. at. the necks 68so as to secure pins 64 to mold kclosure plug 22.V

The slide plate VV6() can be slid quickly so that the circular portions of slots 701are aligned with pins 64, thereby releasing mold closureV plug 22` from the pins 64. Thismay be actuated by a sensing mechanism 71 having a follower`72 and an air cylinder 73V having an externally projecting piston-rod 741for sliding' slide plate 60, both mounted'on the frame of lower pinch rolls 30. Follower 72 yenters opening 47 in mold closure plug 22 ywhenthe mold closure plugV reaches thelower'pinch rolls 30 as shown ink dotted line positions 22b. Sensing mechanism 71 causes the piston rod 74 to strikeslide rplate 6i) of Y This moves the slide plate to a posi-tion in which plug 22 is release-d from chill plate 63 and the attached casting. Such a mechanismis t-ullyy described inthe copending application of Justin E.' Foldessy and Francis Gallucci, SerialNo. 333,383, 'led Decembe; 2,6, 1963,66w Patent No. 3,266,104, issued August 16,.

Mold closure plug 22 is secured in its initial position in the lower end of mold 20 by tie rods 76 and wing nuts 77 prior to the pouring of molten metal into the upper end of mold 20. Tie rods 76 are supported by horizontal members extending between the opposite sides of mold 20. Tiel rodsy 76 have horizontally projecting tines 78 at the lower ends thereof for supporting the heads 66 of pins 64. Mol-d 20 and mold closure plug 22 are secured together by tie rods 76 before the mold 20 is put into position above guide rolls 24.

An apparatus for bringing rmold 20 4and mold closure plug 22 into casting position is shown in FIGS. 5 and 6. This apparatus includes a rail car 88 traveling on tracks 90. Preferably a pair of cars 88 and 88a, both on track Y 90, are used in order to hold the idle time between cast- A pre-assembled mold 20 and mold closure plug with beams 92 and frame 20a is lowered on to car 88 by crane Jacks 94 areV 95 fwhile said car is in the position 88a.

raised to support beams 92 as shown at 94a. Car 88 is ybrought into position so that .the mold 20 is directly above the guide rolls 24. Then jacks 94 are lowered. As jacks 94 are lowered, the -mold frame 20a of mold 20 comes to rest upon the oscillator frame 96, which permits periodic raising and lowering of the mold while the casting is being formed. Such mold oscillators are known in the art and will not be described here. Mold frame 20a comes to rest on oscillator frame 96 before jacks 94V reach their lowermost position. Thus jacks 94 are out of contact with the beams 92, while mold 20 through frame 20a is raised and lowered on oscillator frame 96 during a casting. In this way, the vibrations of the mold 20 are not transmitted to car 88.

Alternatively, a pre-assembled mold 20 and mold closure plug 22 can be brought into casting position by a conventional crane.

' When mold 20 and mold closure plug 22 secured thereto are brought into place prior to the start of a casting, thelower end of plug 20 is in position for engaging chains 34. Chains 34 are then rotated until a pair of lugs 36 enter indentations 47. The chains 34 .are stopped. This is conveniently ldone by a suitable automatic device including a clutch for disengaging the motor driving unit from the chain drive mechanism 32' when the lugs strike shoulders 49 at the lower ends of indentations 47. Such devicesare known in the art. Wing nuts 77 .are then unfrastened and tie rods 76 removed. When the Vwing nuts 77 Vand rods 76fare removed, the chains 34 are moved slightly to a predetermined limit to break the plug seal, after which they chains are reversed to move the lugs 36 to contact the bottom face of block 52.4 Mold closure plug 22 still closes the lower end of mold 20, but is now supported solely by chain conveyor mechanism 32. The mold 20 and mold closure plug 22 are now ready for pouring of molten metal. A bottom pour ladle 98 is brought into position so 'th-at its nozzle is directly over the open upper end of mold 29. Metal is then poured into mold 20.' When the molten metal has'reached a predetermined level near the top of mold 20, the chain conveyor mech; anism 32 is started, causing mold closure plug 22 and the attached casting to be lowered at predetermined speed. When mold closure plug 22 reaches upper pinch rolls 28, the pinch rolls control furthe-r descent of the casting. Pinch .-rolls 28 rotate at such a speed that the linear speed of the casting is the same whether it is controlled by chains 34 or by the pinch rolls. IMold closure plug 22 is disengaged from chains 34 and then disconnected from the attached casting as previously indicated. After disconnection of the mold closure plug from the casting, the plug may be lowered by any desired means, and may then beV inserted in a mold which is then ready for usein forming v place.

closure plug may be further treated as desired.

It is convenient to use two cars 88 and 88a for transporting pre-assembled molds and mold closure plugs into When formation of a casting in mold is completed, car 88 is moved off to dotted line position 88b to the iight, the mold is lifted oit by crane 95a and transported to the place of pre-assembly of a mold closure plug, and car 88a with a pre-assembled mold and mold closure plug is moved into position.

FIG. 7 illustrates a second embodiment of this invention. According to this embodiment of the invention, there is shown a mold closure plug 110 which is adapted to be inserted in the lower end of a conventional continuous casting mold 20. -Mold closure plug 110 has an upper portion 112 which is of small depth and approxi- `mately the same shape las that of the interior of mold 20.

The cross-sectional area of the upper portion of mold closure plug 110 is slightly less than that of the mold 20 so as to permit easy insertion of the plug into the lower end of the mold. Mold closure plug 110 has a lower portion 114 which is of greater cross-sectional area than the upper section 112. A shoulder 116 between the upper 'and lower portions 112 and 114 respectively is adapted to contact the lower end of mold 20 and thereby limit Vthe depth to which mold closure plug 110 can be inserted into mold 20.

The upper end of mold closure plug 110 has a chill plate 118 removably mounted thereon, and -a plurality of upstanding pins 120 having enlarged heads for forming an interlocking grip with the solidied lower end of the casting which is formed in mold 20. The lower end of the casting solidies while the casting is still in the mold. Such construction of chill plate and interlocking pins is ydescribed in more detail and claimed in the copending application of Sigmund L. Andrzejak and Robert J. Keene, Serial No. 291,209, filed June 27, 1963 now Patent l,No. 3,262,161, issued July 2.7, 1966.

Mold closure plug 110 has a pair of indentations 122in the sides thereof for engaging lugs 36 in the chain 34,

Awhich controls the rate of descent and supports the weight Aof the plug and attached casting.

These indentations comprise downwardly and inwardly sloping side Walls 124 and shoulders 126 at the bottom. A pair of recesses 128 in the side walls contain bumper blocks 130` which are spring pressed outwardly by compression springs 132 and limited in their outward movement by retaining plates 134.

. The rate of descent of the mold closure plug and attached casting above the pinch rolls is controlled by chain .conveyor mechanism 32, which includes a pair of chains 34 having lugs'36 for engaging mold closure plug 110, upper sprockets 38, and lower sprockets not shown. This lchain conveyor mechanism 32 is identical to that shown in FIG. 1. The apparatus of this embodiment also includes guide rolls, cooling -means and pinch `rolls similar Ato those shown in FIG. 1.

Mold closure plug 118 is secured to mold 20 by ltie rods 76 and wing nuts 77 prior to positioning the mold in ymolten metal into the mold.

FIG. 8 illustrates a third embodiment of the present 4invention particularly adapted for slabs of relatively great thickness requiring support along the edges in the cooling zone below the mold. Referring now to FIG. 8, Ztl is an open-ended continuous casting mold which may be of conventional construction. The lower end of mold 20 is closed by mold closure plug 148 when molten metal is being poured into the mold. Below rnold 20 is a cooling zone indicated generally at 150 and comprising a plurality of cooling Water sprays 152, a motor driven roll -assembly 154 immediately below mold 20, a plurality of cylindrical guide rolls 156 bearing against the opposite faces of the casting and journaled in roll chocks 158, and a plurality of edge rolls 160 for guiding the two edges of the casting and journaled in edge roll frames 162. Edge roll frames 162 are reciprocably mounted so that they can be reciprocated toward and away from the path of the casting by fluid cylinders 164. Below the cooling zone are upper and lower pinch rolls 28 and 30 respectively for controlling the rate of descent of the casting. A vertically traveling basket 1-65 below lower pinch rolls receives the mold closure plug 148 after it descends below the pinch rolls, and may also be used to lower lengths of casting.

The embodiment of FIG. 8 also includes a chain conveyor mechanism indicated generally at 168 for engaging the mold closure plug 148 and for controlling the rate of descent of said mold closure plug and the attached casting prior to the time the mold 4closure plug reaches upper pinch rolls 28. The chain conveyor 168 of this embodiment includes a pair of link chains 170 having a plurality of outwardly extending lugs 172 at regular intervals, each of said lugs being located between two successive links in the chain, a pair of upper sprockets 174 located near the upper end of the cooling zone, and a pair of lower sprockets 176 located a short distance below lower pinch rolls 30. One of these pairs of sprockets is motor driven and the other pair are idler sprockets; for convenience the lower sprockets 1'76 may be motor driven. Lower sprockets ,176 are located directly below upper sprockets 174, and both sets of sprockets are of the same diameter.

The mold closure plug 148 is rectangular in cross section, having a shape approximately the same as that of the interior of mold 20 and being slightly smaller in crosssectional area so that the mold closure plug 148 readily ts inside mold 20. The length of mold closure plug is substantially less than the distance from the bottom of mold 28 to upper pinch rolls 28. A-t the bottom of mold closure plug 148 are a pair of ears 180 which extend downwardly and outwardly from the rectangular portion of the mold closure plug. The entire mold closure plug 148 including ears 180 is of uniform thickness. The ears 18) have outwardly extending flanges 1182 which provide indentations 183 therebelow for receiving a pair of chain lugs 172. The ears also have horizontally extending recesses 184 located below said ange 182. Tongues .186 having stems 187 attached thereto and extending exteriorly of ears 180 are reciprocable in recesses 184. These tongues 186 are adapted to lock a pair of chain lugs in place in indentations 133. Tongues 186 are beveled along their lower outside surfaces to assist in engagement of mold closure plug 148 with chain lugs 172 when the mold closure plug is lowered onto the chains 170. Tongues 1S-6 are spring pressed outwardly by springs .1188, and outward movement is limi-ted by stops on stems y187 exteriorly of ears 180. Attached to each stem 187 is a horizontal bent U-shaped arm 190 located inwardly from ears 180 with a cam roller 192 on a shaft. The face of each cam roller is mounted at right angle to stern 187. Cam rollers 192 engage cam surfaces 194 to retract tongues 186 and release mold closure plug 148 from chains 170 when the mold closure plug descends below lower pinch rolls 30. Basket 165 is in its topmost posit-ion a short distance below lower pinch rolls 30 and at approximately the same elevation as the lower end of chain 170 as the mold closure plug 148 and casting attached thereto descend below the lower pinch rolls. As cam surfaces 194 engage cam rollers 192, the basket 165 remains stationary or else is caused to move at a slower speed than that of mold closure plug 148 until the mold closure plug has been disengaged frornchain 170 by the coaction of cam surfaces 194 and cam rollers 192 to casting apparatus prior to the start ofv a casting. Amold closure plug is of greater lengththan the mold it-V be similar vto those described in the copending applica tion of Harold G. Frostick, Ser. No. 262,784, tiled March 4, 1963, now Patent No. 3,196,500, issued July 27, 1965. Cam surfaces 1194 kare actually sloping sides of blocks 2195 which have flat upper ends. A block 196 located between the two blocks 195 also has a ilat upper end higher than the upper end of block-s 195. The flat upper end of` block 196 is for supporting the plug 148 as well as Vlength-s of casting in the event the casting is lowered on basket 165. Blocks 195 can be adjusted sideways to lregulate the retracting tongues 186.V The U-shaped arms 19t) and the plug 148 are tilted away from the cam surfaces 194 and basket 165f-or discharging the plug horizontally by means of a tiltmg mechanism (not shown).

Mold closure plug 148 and mold 20 are pre-assembled in telescoping relationship at a location remote from the The self, and thefears 1-80at ,the lowerend of the mold closure plug extend below the bottom of the mold and at the same time the top of the mold `closure plug 148 isk Mold closure plug 148 is then lowered into metal casting 1 plug 210 from the chain.

positionjwith the .top of the plug just inside the bottom ofV the mold 20. The .metal casting position of mold closure plug 1148V is shown in` solid lines in FIG. 8. `The Y motor driven roll assembly 154 is used to lower mold 'closure plug 148 from position 148a telescoped inside rtollsr2il0, journaled in frame 201 and driven by motor.

202.y On thefopposite side of the casting is a plurality of ychain links 216 directly as will be hereinafter described.

Mold closure plug 210 is preferably of rectangular shape and slightly smaller in cross-sectional area than the interior of the mold so as to permit telescoping therein. Plugr210 has a pair of ears 220 at itslower end which extend downwardly and outwardly beyond the rectangular portion of plug 210. These ears 220 are provided With outwardly extending flanges 222 having indentations 223 for receiving chain links 216. Ears 220 also have laterally extending recesses 224 with reciprocable tongues 226 therein below indentations 223. Tongues 226 are biased outwardly by compression springs 228. Stems 230 extending cxteriorly of ears 220 and having stops 232 thereon are attached to tongues 226. Bent `arms 234 located exteriorly of the casting and attached to stems 230 provide for disengagement of -mold closure Cam rollers 236 are mounted on shafts and the face of each cam roller is at right angles to stem 230. For releasing the plug 210, the cam rollers 236 contact the cam surfaces in the same way as in the embodiment shown in FIG. 8. The motor driven roll assembly 154, guide rolls 156, and guide roll chocks 158 are also the same as in the embodiment of FIG. 8.

Several embodiments of the invention have been described for purposes of illustration. While these differ in various details, they are similar in every case in that the length of the mold closure plug is substantially less than the distance between the'bottom of the mold and the upper pinch rolls. The greatly reduced length as compared to the conventional starter bar, which extends clear from the bottom ofthe mol-d to the upper pinch rolls when in metal casting position, makes it possible to make the mold f formed and pinch roll means located at a substantial disidler rollsp20i3, journaled in frame 20'4'which can be 'Y reciprocated horizontallyby uid cylinders 205.

When -mold closure vplug 148 isfbeing lowered to the Y casting'position, edge rolls 160 and `frame 162 above until the chain lugs 172 enter the indentations 1'83 in ears y 180. Lugs172 c-ause tongues V186 to retract by riding on the beveled surfaces of the tongues. The tongues then snap Y :shut and lock chain lugs 172 in engagement with the mold closure plug 148'. The mold closure plug is now ready ito be lowered when the level of molten metal in the mold has reached its desired maximum.

FIG. 12 shows another embodiment of the present invention.` According to this embodiment, there is a mold closure plug 210 and a chain conveyor mechanism 212 Y for lowering this plug from metal casting position in the Y lower. end Vof mold 20. The chain conveyor mechanism according to kthis embodiment of the invention comprises a pair of chains 214 having a plurality of links 216.and traveling over a pair of upper sprockets 218 and a pair of lower `sprockets not shown. There yare no lugs in chains 214 as provided in the chains of the other three embodiments of the invention. Mold closure plug 210 engagestance below said lmold for controlling the rate of descent of said casting, the improvement comprising a unitary 4mold closure plug adapted to be inserted into the lower end of said mold, the length of said plug being substantially less than the distance betweenthe bottom of said ported by said pinch roll means until said plugis in contact with said pinch roll means, and power driven means laterally displaced from the path of said plug for supporting the plug and for controlling the rate of descent thereof as said plug descends from its initial position in the lower end of said mold to said pinch roll means.

2. Apparatus according to claim 1 in which said power driven meanscomprises a pair of endless chains on either side of the path of said Vmold closure plug.

3. Apparatus according to claim 2 in which said mold closure plug includes spring pressed laterally movable members adapted to engage said chains in locking engagement.

4. Apparatus according to claim 2 in which said chains have a plurality of outwardly projecting lugs and said rnold closure plug includes a pair of indentations in side walls thereof, said indentations including sloping walls permitting entry of a pair of chain lugs, said plug also including laterally movable-spring pressed members for retaining said lugs in said indentations. v

5. Apparatus according to claim 2 in which said mold closure plug includes a pair of outwardly extending flanges and a pair of laterally movable spring pressed members rfor engaging said chains therebetween.

6. Apparatus according to .claim 2 in whichthe paths 9 of said chains diverge at the lower ends thereof to release said mold closure plug.

7. Apparatus according to claim 2 including spring pressed laterally movable means in said mold `closure plug for engaging said chains in locking engagement and cam means for moving said laterally movable means -to a position for releasing said plug from said Ichains.

References Cited by the Examiner UNITED STATES PATENTS 10 Williams 22-57.2 Schoppee 198-164 Muller et al. 1 22-57.2 Schneckenburger et al.

I. SPENCER OVERHOLSER, Primary Examiner.

R. S. ANNEAR, Assistant Examiner. 

1. IN A CONTINUOUS CASTING APPARATUS INCLUDING A SUBSTANTIALLY VERTICAL OPEN-ENDED MOLD IN WHICH A CASTING IS FORMED AND PINCH ROLL MEANS LOCATED AT A SUBSTANTIAL DISTANCE BELOW SAID MOLD FOR CONTROLLING THE RATE OF DESCENT OF SAID CASTING, THE IMPROVEMENT COMPRISING A UNITARY MOLD CLOSURE PLUG ADAPTED TO BE INSERTED INTO THE LOWER END OF SAID MOLD, THE LENGTH OF SAID PLUG BEING SUBSTANTIALLY LESS THAN THE DISTANCE BETWEEN THE BOTTOM OF SAID MOLD AND SAID PINCH ROLL MEANS, SAID PLUG BEING UNSUPPORTED BY SAID PINCH ROLL MEANS, SAID PLUG BEING CONTACT WITH SAID PINCH ROLL MEANS, AND POWER DRIVEN MEANS LATERALLY DISPLACED FROM THE PATH OF SAID PLUG FOR SUPPORTING THE PLUG AND FOR CONTROLLING THE RATE OF DESCENT THEREOF AS SAID PLUG DESCENDS FROM ITS INITIAL POSITION IN THE LOWER END OF SAID MOLD TO SAID PINCH ROLL MEANS. 